Conventional concrete floors are common in nonresidential buildings and multi-family residential buildings including both structural steel buildings and masonry wall buildings. These buildings include office buildings, nursing homes, schools, apartments, and any other buildings having above-ground floors which span extended lengths.
With a conventional concrete floor system, the building is comprised of structural steel support beams and steel floor joists. The structural steel beams provide support for the steel floor joists and the steel floor joists span the distance between the steel support beams. A metal deck is placed on top of the steel floor joists and becomes the form support for the concrete floor. Reinforcement bar and wire mesh may be placed on top of the metal deck to provide additional structural strength to the concrete. Next, wet concrete is poured on top of the metal deck and allowed to harden thereby forming a concrete slab. The depth of the concrete slab is typically a minimum of four inches.
Most buildings will require a minimum fire rating which indicates a certain resistance to fire damage. In conventional systems, the steel floor joists, which provide the structural strength to support the concrete slab, remain exposed to the floor below. Hence, a subsequent fire retarding material must be applied, or an appropriate ceiling board constructed, to protect the exposed steel floor joists. Conventional concrete slabs also provide limited insulation and sound attenuation properties. Additionally, any formwork used when pouring the concrete, other than the metal deck, must be removed, which can be labor intensive and can result in higher costs being associated with the construction of these types of concrete slabs.
In seeking better materials for constructing floors of a building, several forms of insulated deck structures have been suggested. One such example of a deck structure is disclosed in U.S. Pat. No. 4,090,336 to Carroll which discloses an insulated floor and roof deck structure. The structure has a plurality of sub-purlins supported on structural members. Gypsum formboard and synthetic organic polymer foam are prepared in panels and supported on the flanges of the sub-purlins. Following installation of the gypsum formboard and polymer foam assembly, concrete is poured to a suitable thickness to form a unitary structure. The concrete flows around the sub-purlins and comes into contact with the gypsum coreboard and, after the concrete dries, a composite structure which provides resistance to deflections is formed. The top of the sub-purlin extends above the top surface of the foam and is very close to the upper surface of the concrete poured thereover. Thus, as taught by the patent, the sub-purlin is an integral structural part of the deck structure and provides structural strength to support loads which could not be supported by the concrete alone. Because the sub-purlins are exposed and provide structural support to the deck structure, steps must be taken to fireproof the sub-purlins so that a desired fire rating can be attained.
In U.S. Pat. No. 716,628 to Dickey a fireproof flooring is disclosed which includes steel floor beams supporting a series of previously molded concrete slabs bridging the space between the beams. A core of loose cinders is shoveled onto the slabs so as to largely fill the space between the beams. A bed of concrete is then applied over the cinders and into the recesses adjacent to the beams. Under modern fire codes, however, additional fire proofing would have to be installed over the beams to receive a certain fire rating.
U.S. Pat. No. 3,320,704 to Forsythe, et al. discloses a roof deck including a series of sub-purlins welded to the top of a series of I-beam purlins to form a grid. The sub-purlins are generally hollow and open from the top. Expanded metal lath strips are vertically positioned in the sub-purlins and extend through the slots therein. Wire mesh is supported on the cradles of lath strips and gypsum concrete fills the sub-purlins and extends through the slots. The gypsum concrete embeds the wire mesh and lath strips to form a monolithic structure. The concrete between the sub-purlins is supported by a plurality of removable form elements. The concrete is poured into the hollow box section of the sub-purlins to provide a composite member for the roof deck structure. The roof structure according to this patent would also require additional fire proofing and insulation.
Thus, there is a need for improved building materials for use in the construction of insulated deck structures. Such a deck structure must be capable of being efficiently installed to reduce labor costs while at the same time providing adequate insulation properties and sound attenuation. In particular, such a deck structure should be able to achieve a certain desired fire rating without the necessity of additional fireproofing procedures or materials.